1. Field of the Invention
The present invention relates to a communication device, and in particular to a communication device for performing communications between a user terminal and a network service provider apparatus.
An Internet/intranet access system charged on an as-used basis realized by a dial-up utilizing an ISDN or a telephone line has been rapidly shifting towards a system charged on a fixed-price basis similar to a system utilizing a leased line yet being inexpensive due to the advent of new high-speed transmission technologies such as an ADSL (Asymmetric Digital Subscriber Line)/FTTH (Fiber To The Home) or the competition heat-up among carriers.
A service for a general home firstly requires easy network connections, so that an Ethernet is preferable as an interface provided for users. On the other hand, an ISP (Internet Service Provider) providing an Internet connection service requires that the user management is performed by the same mechanism as a conventional dial-up system such as point-to-point protocol (PPP).
In order to satisfy these two requirements, has been devised a PPPoE (PPP over Ethernet) encapsulating the PPP on the Ethernet, which is prescribed by the document RFC2516 of the IETF (Internet Engineering Task Force). The service utilizing this technology is receiving attention in countries of the world.
2. Description of the Related Art
An access line applying thereto the ADSL or the FTTH has a mechanism that a user side device cannot access the devices other than the carrier devices. However, in the future, developments are expected of an Ethernet access network carrying the Ethernet directly on an optical fiber to perform switching on a utility pole and the like.
Such an Ethernet access network has an arrangement shown in FIG. 1 which will be specifically described later. Namely, user terminals 11 and 12 are connected to an edge device 18 which is an ISP terminal respectively through ONU's 13 and 14 as well as a communication device 15. The user terminals 11 and 12 access the Internet INET through the edge device 18.
In consideration of security, this network uses a technology such as a VLAN (Virtual LAN) defined by the IEEE802.1Q to prevent the user terminals 11 and 12 from accessing devices other than the edge device 18.
Namely, while the Ethernet inherently enables a direct communication with e.g. a personal computer of a next door, it is possible that a malicious third party if any would steal a glance at a frame or access the network using another person's ID.
Since it is difficult to take defensive measures thereof especially for a beginner or the like who does not have knowledges concerning security, the mechanism is provided such that communications are made through the edge device 18 providing security measures.
With the above-mentioned mechanism using the above noted PPPoE, in order that the user terminal 11 communicates with the user terminal 12, a frame 23 once flows to the edge device 18 through the ONU 13 and the communication device 15, and then returns therefrom for the communication. Moreover, when the user terminals 11 and 12 have respectively subscribed to different ISP's, the communication is made through the Internet.
This is not only a waste of the bandwidth, but also results in such a problem that the load of the edge device 18 is increased. In the future, the ratio of the communication between the devices at a physically short distance from each other is expected to increase due to widespread of online games, the advent of applications stuck on community, and network support of various apparatuses.
However, in the extension of the current system, if the available bandwidth per user terminal is increased by 10 times, a simple calculation shows that an edge device with a processing performance of 10 times the current state multiplied by a number of users will be required.
Therefore, if the system utilizing the Ethernet is simply constructed, the above-mentioned problem of security arises, so that a mechanism is required to enable a shortcut communication (communication not through the edge device 18) maintaining the current security level.
Namely, in order to perform the shortcut communication not through the edge device 18 without constructing a system between the user terminals, the communication device 15 mutually connecting the user terminals 11 and 12 is required to transmit a frame received from the user terminals 11 and 12 directly to the destination user terminal without transmitting it to the edge device 18.